The ‘Prepared Salads’ industry produces a ‘ready to eat’ product. Therefore, consumers expect these products to be safe, convenient and free from foreign bodies and/or contaminants. However, the nature of outdoor salad crop production means that there is an ever-present risk of contamination in the raw materials grown for prepared salads. This contamination can take many forms, but, notably, includes the presence of insects (pests and ‘casual intruders’) or other invertebrates, including organisms that alight on crop stands, for example, or which can fall into or otherwise be included in the processing chain.
At present, no comprehensive method exists to detect and remove these contaminants. The industry's current approach relies on a series of (imperfect) ‘hurdles’ designed to reduce the likelihood of insect contamination. These hurdles include harvester design (riddle belts, air separators etc.) and some (factory based) vision equipment. However, most operations rely primarily on manual inspection and removal. The inherent weaknesses of this approach and increasing labour costs are requiring processors to look towards other technologies.
A number of vision systems are in commercial operation. These tend to be based on visible and/or infra-red light and utilise conventional cameras together with software capable of interpreting the images received. Recent advances in (notably) software development have made a number of systems commercially viable. However, this equipment still has significant drawbacks: Differentiation between ‘good’ and ‘bad’ material is insufficient—leading to a high level of ‘false positives’, leading to unnecessary loss of otherwise good product, or inadequate rejection rates, resulting in contaminated product. Also, even with the most sophisticated equipment, ‘shadowing’ takes place where contaminants are shielded by crop material.
Metal detectors and X-ray scanners are established technologies which can effectively recognise foreign bodies on the basis of electrical properties or density. However, technologies for detecting foreign bodies, such as insects, wood, and plastics, are limited and there is significant potential for improvement. The dietary imperative to increase fruit and vegetable consumption has put new focus on the consumer acceptability of fresh fruit and vegetable produce, including elimination of insects from fruit and vegetable crops, a task made more important by the concomitant consumer pressure to reduce pesticide use. The most challenging task is perhaps the detection of insect fragments in bagged leaf salads.
Further background prior art can be found in:    “Infrared and Raman microspectroscopy of foreign materials in tissue specimens” Kalasinsky, K S; Kalasinsky, V E, Spectrochimica Acta part A—Molecular and Biomolecular Spectroscopy Vol 61 Iss 7Pps: 1707-1713, 2005    “Raman microspectroscopic studies of amber resins with insect inclusions”, Edwards, H G M, Farwell, D W; Villar, S E J, Spectrochimica Acta part A—Molecular and Biomolecular Spectroscopy Vol 68 Pps: 1089-1095, 2007    “Potential of Near-Infrared Fourier Transform Raman Spectroscopy in Food Analysis” Ozaki, Y. Cho, R., Ikegaya, K., Muraishi, S., Kawauchi, K. Applied Spectroscopy, Vol 46, Iss 10, pp. 1503-1507, 1992    “Insect monitoring with fluorescence lidar techniques: field experiments”, Guan et al., Applied Optics, Vol. 49, No. 27, pp. 5133-5142, in which required the capture of test species, dusting with characteristic fluorescent dye powders, and then monitoring the thus treated insects after release.    U.S. Pat. No. 6,770,453, “Methods of Detecting Chitinous Material in Non-Chitinous Biological Material”.    U.S. Pat. No. 7,288,768, “Method for Measuring the Amount of an Organic Substance in a Food Product with Infrared Electromagnetic Radiation”.    U.S. Pat. No. 5,118,610, “Techniques for Detecting Insect Contamination of Foodstuffs”, which utilizes a biochemical assay to detect chitin.    U.S. Pat. No. 7,787,111, “Simultaneous Acquisition of Fluorescence and Reflectance Imaging Techniques with a Single Imaging Device for Multitask Inspection”.    U.S. Pat. No. 6,587,575, “Method and System for Contamination Detection during Food Processing”.
There remains, however, a long felt need for new sensing technologies to provide an enhanced level of detection in food handling and other environments to detect and remove insect and other contaminants.